21 March 2016

Electron pairs superconduct in NbSe2 layer at high fields

Cooper pairs in a monolayer of niobium diselenide Cooper pairs in a monolayer of niobium diselenide

Niobium diselenide is found to retain its superconductivity even under very high magnetic fields.

First, some background

A superconductor is a material that, under the right conditions, conducts electricity with perfect efficiency. Electrons zoom through it with zero energy loss, behaving very differently than they do in a regular conductor such as copper. In conventional superconductors, electrons team up in what are called Cooper pairs, spinning top-like in opposite directions (what physicists call spin up and spin down)

Superconductivity only occurs under certain conditions, and can be killed if the temperature is too high or within a high magnetic field, which forces electrons to align with it, rupturing the Cooper pairs.

What did scientists discover?

Studying a single layer of the superconductor niobium diselenide (NbSe2) within a very high magnetic field, scientists found its superconductivity persists to much higher magnetic fields than would normally be predicted. Using just a single layer of the material restricts the electrons to two dimensions.

What makes monolayer NbSe2 unique is that it forms electron pairs in such a way that electron spins are essentially locked in place (indicated by red arrows in the accompanying figure) by an interaction between the spins and the material itself. This effect is enhanced as the material is thinned to three, then two, then the single layer depicted in the figure.

Why is this important?

Superconductivity holds great technological promise. Understanding the physics dictating the behavior of these materials is critical to moving them out of the laboratory and into the realm of practical use as technological building blocks in much the same way as semiconductors are currently used.

Who did the research?

X. Xi1, Z. Wang1, W. Zhao1, J.-H. Park2, K.T. Law3, H. Berger4, L. Forro4, J. Shan1, K.F. Mak1

1Penn State University; 2National High Magnetic Field Laboratory; 3Hong Kong University of Science and Technology; 4Ecole Polytechnique Fédérale de Lausanne

Why did they need the MagLab?

THE TOOLS THEY USED

This research was conducted in the 31 tesla magnet in the DC Field Facility.

The low temperatures and extraordinarily high magnetic fields needed to break the superconducting pairs in NbSe2 required that the experiments be done at the MagLab. Further work on this material in the 45 tesla hybrid magnet is planned.

Details for scientists

Funding

This research was funded by the following grants: G.S. Boebinger (NSF DMR-1157490); K.F. Mak (DOE DESC0013883); J. Shan ( DOE DESC0012635, NSF DMR-1410407); K. T. Law (HKUST3/CRF/13G, CIG); L. Forro (Swiss NSF); Z. Wang (NSF DMR-1420451)


For more information, contact Tim Murphy.

Details

  • Research Area: Superconductivity - Basic
  • Research Initiatives: Materials
  • Facility / Program: DC Field
  • Year: 2016
Last modified on 21 March 2016